Catalyst composition containing bidentate coordinated trivalent group IVB metal complex for preparing syndiotactic vinyl aromatic polymer

ABSTRACT

A novel trivalent Group IVB metal complex for preparing syndiotactic vinyl aromatic polymers is disclosed which is coordinated by a bidentate ligand and is represented by the formula (I): 
     
         (C.sub.5 R.sub.n H.sub.5-n)M(BD).sub.m Y.sub.p             (I) 
    
     wherein C 5  R n  H 5-n  is a substituted or unsubstituted cyclopentadienyl group, n is an integer between 0 and 5, and R is C 1  to C 12  alkyl, aryl, substituted alkyl, or substituted aryl; M is a trivalent Group IVB metal; (BID) is a bidentate ligand with -1 valence, having a coordinating group which is capable of forming a coordinating bond or a chelating bond with the metal M; Y is selected from the group consisting of alkyl, aryl, aralkyl, halogen and hydrogen; m is an integer of 1 or 2; and m+p=2.

This is a divisional application of application Ser. No. 08/881,683filed Jun. 23, 1997, now U.S. Pat. No. 5,869,721.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel bidentate coordinated trivalentGroup IVB metal complex, and, more particularly, to a process forpreparing syndiotactic vinyl aromatic polymers using the bidentatecoordinated trivalent Group IVB metal complex as a catalyst.

2. Description of the Prior Art

Vinyl aromatic polymers, or vinyl aromatic compound-containing polymersin general, can be classified into three categories: atactic, isotactic,and syndiotactic. The vinyl aromatic polymers having a syndiotacticconfiguration have many advantageous properties than the atactic andisotactic counterparts. For example, syndiotactic polystyrenes exhibitthe advantages of having high melting point (about 270° C.), low density(about 1.04 kg/cm³), low dielectric constant (about 2.6), high vicatsoftening temperature (about: 254° C.), excellent chemical resistanceand water (steam) resistance, and low moisture absorption. The abovereported values are measured from a specific syndiotactic polystyreneunder a specific set of conditions. These values, of course, are subjectto change as a result of different polymer molecular weight and manyother factors.

In recent years, a trivalent titanium-based catalyst containingcyclopentadienyl as a ligand has been used for preparing syndiotacticvinyl aromatic polymers. For example, WO 95/10551 discloses a trivalenttitanium-based catalyst composition for preparing syndiotactic vinylaromatic polymers. Such catalyst composition includespentamethylcyclopentadienyl titanium(III) dimethoxide [Cp*Ti(OMe)₂, inwhich Cp* represents pentamethylcyclopentadienyl and Me representsmethyl], a borate, and a hydrocarbylation agent. In addition, EuropeanPatent No. 0,655,467 discloses the use of another trivalenttitanium-based catalyst for preparing vinyl aromatic polymers.

However, the above-mentioned catalysts suffer from a number ofshortcomings in that the catalyst has undesirable catalytic activity,inferior stereoselectivity, and the polymer so obtained exhibits anundesirably broad molecular weight distribution.

SUMMARY OF THE INVENTION

The primary object of the present invention is to solve theabove-mentioned problems by providing a novel trivalent Group IVB metalcomplex for use in preparing vinyl aromatic polymers with highsyndiotacticity. The trivalent Group IVB metal complex of the presentinvention is coordinated by a bidentate ligand with -1 (minus one)valence, such that the metal complex is stabilized by the coordinatingor chelating bond between the trivalent Group IVB metal and thebidentate ligand. By using the bidentate coordinated Group IVB metalcomplex disclosed in the present invention as a catalyst for preparingvinyl aromatic polymers, the catalytic activity and stereoselectivitycan be enhanced, and the polymer so produced has a narrower molecularweight distribution.

In the the present invention, a novel bidentate coordinated metalcomplex is disclosed which is represented by the following formula (I):

    (C.sub.5 R.sub.n H.sub.5-n)M(BD).sub.m Y.sub.p             (I)

wherein:

C₅ R_(n) H_(5-n) is a substituted or unsubstituted cyclopentadienylgroup, n is an integer between 0 and 5, and R is C₁ to C₁₂ alkyl, aryl,substituted alkyl, or substituted aryl;

M is a trivalent Group IVB metal;

(BD) is a bidentate ligand with -1 valence, having a coordinating groupwhich is capable of forming a coordinating bond or a chelating bond withthe metal M;

Y is selected from the group consisting of alkyl, aryl, aralkyl, halogenand hydrogen;

m is an integer of 1 or 2; and

m+p=2.

DETAILED DESCRIPTION OF THE INVENTION

The present invention discloses a novel bidentate coordinated metalcomplex which is represented by the following formula (I):

    (C.sub.5 R.sub.n H.sub.5-n)M(BD).sub.m Y.sub.p             (I)

wherein:

C₅ R_(n) H_(5-n) is a substituted or unsubstituted cyclopentadienylgroup, n is an integer between 0 and 5, and R is C₁ to C₁₂ alkyl, aryl,substituted alkyl, or substituted aryl;

M is a trivalent Group IVB metal;

(BD) is a bidentate ligand with -1 valence, having a coordinating groupwhich is capable of forming a coordinating bond or a chelating bond withthe metal M;

Y is selected from the group consisting of alkyl, aryl, aralkyl, halogenand hydrogen;

m is an integer of 1 or 2; and

m+p=2.

In a preferred embodiment of the present invention, the values of m andp are 2 and 0, respectively, and the metal complex is represented by (C₅R_(n) H_(5-n))M(BD)₂. In this embodiment, the bidentate coordinatedmetal complex of (C₅ R_(n) H_(5-n))M(BD)₂ can be prepared by a processwhich includes the step of reacting (C₅ R_(n) H_(5-n))MCl₂ with (BD)Li.The symbols R, n, M, and (BD) have the same definition as thosedescribed above.

As discussed above, the coordinating group contained in the bidentateligand (BD) is capable of forming a coordinating bond or a chelatingbond with the trivalent group IVB metal M. The preferred embociments ofthe coordinating group include nitrogen, phosphorus, oxygen, ether, orthioether.

Representative examples of the bidentate ligand (BD) includes: ##STR1##wherein R¹ is alkyl having from 1 to 6 carbon atoms. As defined earlier,M is a trivalent Group IVB metal, which can be titanium, zirconium, orhafnium, preferably titanium.

The group C₅ R_(n) H_(5-n) is a substituted or unsubstitutedcyclopentadienyl group. Preferably C₅ R_(n) H_(5-n) is η⁵-cyclopentadienyl or η⁵ -pentamethylcyclopentadienyl.

Representative examples of the bidentate coordinated metal complex ofthe present invention include:

(η⁵ --C₅ H₅)Ti(C₆ H₄ --o--CH₂ NMe₂)₂ ;

(η⁵ --C₅ Me₅)Ti(C₆ H₄ --o--CH₂ NMe₂)₂ ;

(η⁵ --C₃ H₅)Ti(CH₂ C₆ H₄ --o--NMe₂)₂ ;

(η⁵ --C₅ Me₅)Ti(CH₂ C₆ H₄ --o--NMe₂)₂ ;

(η⁵ --C₅ H₅)Ti(OC₆ H₄ --o--NMe₂)₂ ;

(η⁵ --C₅ Me₅)Ti(OC₆ H₄ --o--NMe₂)₂ ;

(η⁵ --C₅ H₅)Ti(C₆ H₄ --o--OCH₃)₂ ;

(η⁵ --C₅ Me₅)Ti(C₆ H₄ --o--OCH₃)₂ ;

(η⁵ --C₅ H₅)Ti(9-hydroxy-N,N-dimethyl-1-naphthyl amine)₂ ;

(η⁵ --C₅ Me₅)Ti(9-hydroxy-N,N-dimethyl-1-naphthylamine)₂ ;

(η⁵ --C₅ H₅)Ti(8-hydroxyquinoline)₂ ;

(η⁵ --C₅ Me₅)Ti(8-hydroxyquinoline)₂ ;

(η⁵ --C₅ H₅)Ti(acetylacetone)₂ ; and

(η⁵ --C₅ Me₅)Ti (acetylacetone)₂ ;

wherein η⁵ --C₅ H₅ represents a cyclopentadienyl group, Me represents amethyl group, and η⁵ --C₅ Me₅ represents a pentamethylcylcopentadienylgroup.

The bidentate coordinated metal complex of the present invention can becombined with an activating cocatalyst to form a catalyst composition,which can be used for preparing vinyl aromatic polymers with highsyndiotacticity.

The activating cocatalyst can be methyl aluminoxane (MAO), a trialkylaluminum, a dialkyl aluminum, a salt of an inert and non-coordinatinganion, or a mixture thereof.

Preferably, the trialkyl aluminum is selected from the group consistingof trimethyl aluminum, triethyl aluminum, tripropyl aluminum,triisopropyl aluminum, tributyl aluminum, and triisobutyl aluminum(TIBA).

Preferably, the inert and non-coordinating anion is a borate. Examplesof those borates that can be advantageously used in the presentinvention include N,N-dimethyl aniliniumtetrakis(pentafluorophenyl)borate, triphenyl carbeniumtetrakis(pentafluorophenyl)borate, trimethyl ammoniumtetrakis(pentafluorophenyl)borate, ferroceniumtetrakis(pentafluorophenyl)borate, dimethyl ferroceniumtetrakis(pentafluorophenyl)borate, and silvertetrakis(pentafluorophenyl)borate.

Preferably, the activating cocatalyst is methyl aluminoxane, or amixture of a trialkyl aluminum and a borate.

By using the catalyst composition of the present invention, whichcontains the novel bidentate coordinated metal complex of the presentinvention and an activating cocatalyst, syndiotactic vinyl aromaticpolymers can be synthesized. One or more vinyl aromatic monomers can besubjected to polymerization in the presence of a catalytically effectiveamount of the catalyst composition of the present invention.

The suitable vinyl aromatic monomer can be represented by the formula(II) ##STR2## wherein each R² is independently selected from the groupconsisting of hydrogen; aliphatic, cycloaliphatic, aromatic hydrocarbongroups having from 1 to 10 carbon atoms; and halogen atoms. Examples ofsuch monomers include styrene, chlorostyrene, n-butylstyrene,p-vinyltoluene, α-methylstyrene, etc., with styrene being especiallysuitable.

The present invention discloses a novel trivalent Group IVB metalcomplex, which can be used as a catalyst for preparing syndiotacticvinyl aromatic polymers. One of the key elements of the novel metalcomplex of the present invention, is that it contains a bidentate ligandwith -1 valence, which is coordinated to the central trivalent Group IVBmetal, such that the metal complex is stabilized by the coordinating orchelating bond between the trivalent Group IVB metal and the bidentateligand. By using the bidentate coordinated Group IVB metal complex as acatalyst for preparing vinyl aromatic polymers, catalytic activity andstereoselectivity can be enhanced, and the polymer so obtained has anarrower molecular weight distribution than those obtained from theprior art processes.

The following examples are intended to more fully illustrate the processand the advantages of the present invention without limiting its scope,since numerous modifications and variations will be apparent to thoseskilled in the art.

EXAMPLES 1 Preparation of (η⁵ --C₅ Me₅)Ti(C₆ H₄ --o--CH₂ NMe₂)₂

1.27 g of [(C₅ Me₅)TiCl₂ ]_(x) was charged into a 100 mL Schlenk flask,then 50 mL of ether was added and stirred. Thereafter, 1.41 g of (C6H₄--o--CH₂ NMe₂)Li was added slowly at 0° C., and the reddish greensolution was quickly turned into reddish brown. The resulting solutionwas allowed to be in room temperature and the reaction was continued forabout 5 hours. Finally the reaction solution was filtered to removeLiCl, and recrystallized in pentane to obtain 1.5 g of a dark red solid; yield 66%.

EXAMPLES 2 Preparation of (η⁵ --C₅ H₅)Ti(C₆ H₄ --o--CH₂ NMe₂)₂

The same procedures as described in Example 1 were employed except thatthe reactants were [(η⁵ --C₅ H₅)TiCl₂ ]_(x) (0.736 g, 4 mmol) and (C₆ H₄--o--CH₂ NMe₂)Li(1.13 g, 8 mmol). The final product was 0.88 g of a darkred solid; yield 58%.

EXAMPLES 3 Preparation of (η⁵ --C₅ Me₅)Ti(CH₂ C₆ H₄ --o--NMe₂)₂

The sane procedures as described in Example 1 were employed except that(C₆ H₄ --o--CH₂ NMe₂)Li was replaced by (CH₂ C₆ H₄ --o--NMe₂)Li. Thefinal product was a dark reddish brown solid; yield 60%.

EXAMPLES 4 Preparation of (η⁵ --C₅ Me₅)Ti(8-hydroxyquinoline)₂

The same procedures as described in Example 1 were employed except that(C₆ H₄ --o--CH₂ NMe₂)Li was replaced by two equivalents of8-hydroxyquinoline lithium salt. The yield of the final product was 45%.

EXAMPLES 5 Preparation of (η⁵ --C₅ Me₅)Ti(acac)

The same procedures as described in Example 1 were employed except that(C₆ H₄ --o--CH₂ NMe₂)Li was replaced by lithium salt of acetylacetone(acac), and ether was replaced by THF as the solvent. The reaction wasconducted at room temperature for about 5 hours, and, after thereaction, the reaction solution was extracted and recrystallized intoluene to obtain a reddish brown solid.

EXAMPLE 6 Polymerization of styrene

A mixture of 300 mL of an Al₂ O₃ -purified styrene monomer and 3.6 mL ofa 10 wt % methylaluminoxane solution was placed in a 1-liter reactor.The reaction vessel was heated to 60° C. Then 0.0066 mmol of thecatalyst obtained from Example 1 was added, and the reaction wasconducted for 90 minutes. After the reaction was complete, the reactionproduct was washed with a hydrochloric acid/methanol mixture todecompose the catalyst component and dried to obtain 19 g of a resultantpolymer, which was then subjected to Soxhlet extraction under boilingfor 5 hours by the use of methyl ethyl ketone, 17.2 g of the insolublecomponent was obtained. For this resultant syndiotactic polymer, theweight average molecular weight was 2,630,000; the number molecularweight was 1,310,000 and in its thermal differential analysis, themelting point was 271° C.

EXAMPLES 7-10

The same procedures described in Example 6 for preparing syndiotacticpolystyrene were employed except that the catalysts used wererespectively replaced by the catalysts obtained from Examples 2-5. Thesyndiotactic polystyrene obtained from Example 7 was analyzed to have aweight average molecular weight of 184,000, a number molecular weight of98,000, and a molecular weight distribution of 1.87. The other resultswere shown in Table 1.

COMPARATIVE EXAMPLE 1

The same procedures described i n Example 6 for preparing syndiotacticpolystyrene were employed except that the catalyst used was replaced bypentamethylcyclopentadienyl titanium (III) dimethoxide Cp*Ti(OMe)₂. Theresults were shown in Table 1.

The foregoing description of the preferred embodiments of this inventionhas been presented for purposes of illustration and description. Obviousmodifications of variations are possible in light of the above teaching.The embodiments were chosen and described to provide the bestillustration of the principles of this invention and its practicalapplication to thereby enable those skilled in the art to utilize theinvention in various embodiments and with various modifications as aresuited to the particular use contemplated. All such modifications andvariations are within the scope of the present invention as determinedby the appended claims when interpreted in accordance with the breadthto which they are fairly, legally, and equitably entitled.

                                      TABLE 1                                     __________________________________________________________________________                                       Catalytic                                                             Catalyst amount MAO amount Reaction time                                                     activity         Melting                                                       Example      Catalyst                                                        (mmol)       (mL)      (minutes)                                                 (g-sPS/g-Ti · h)                                                  point (° C.)                 __________________________________________________________________________    6     Example 1                                                                            0.0066  3.6    90       4 × 10.sup.4                                                                 271                                   7         Example 2       0.0065       3.6          90        7.2                                                     × 10.sup.4      254                                                      8         Example 3                                                          0.0044       2.4          60                                                      3.1 × 10.sup.4                                                      267                                   9         Example 4       0.0067       3.6          90        5.5                                                     × 10.sup.3      --                                                       10         Example 5                                                         0.0067       3.6          60                                                      4.3 × 10.sup.3                                                      --                                    Comparative  Cp*Ti(OMe).sub.2 0.0044       2.4          60        1.3                                                 × 10.sup.4      266           __________________________________________________________________________

What is claimed is:
 1. A bidentate coordinated catalyst composition forproducing a syndiotactic vinyl aromatic polymer, comprising:(a) abidentate coordinated metal complex represented by the following formula(I):

    (C.sub.5 R.sub.n H.sub.5-n)M(BD).sub.m Y.sub.p             (I)

wherein: C₅ R_(n) H_(5-n) is a substituted or unsubstitutedcyclopentadienyl group, n is an integer between 0 and 5, and R is a C₁to C₁₂ alkyl, aryl, substituted alkyl, or substituted aryl; M is atrivalent Group IVB metal; (BD) is a bidentate ligand with a -1 valence,having a coordinating group which is capable of forming a coordinatingbond or a chelating bond with the metal M; Y is selected from the groupconsisting of alkyl, aryl, aralkyl, halogen, and hydrogen; m is aninteger of 1 or 2; m+p=2; and (b) an activating cocatalyst selected fromthe group consisting of methyl aluminoxane (MAO), trialkyl aluminum,dialkyl aluminum, salts of an inert and non-coordinating anion, andmixtures thereof.
 2. The catalyst composition as claimed in claim 1,wherein the trialkyl aluminum is selected from the group consisting oftrimethyl aluminum, triethyl aluminum, tripropyl aluminum, triisopropylaluminum, tributyl aluminum, and triisobutyl aluminum (TIBA).
 3. Thecatalyst composition as claimed in claim 1, wherein the inert andnon-coordinating anion is a borate.
 4. The catalyst composition asclaimed in claim 3, wherein the borate is selected from the groupconsisting of N,N-dimethyl anilinium tetrakis(pentafluorophenyl)borate,triphenyl carbenium tetrakis(pentafluorophenyl)borate, trimethylammonium tetrakis(pentafluorophenyl)borate, ferroceniumtetrakis(pentafluorophenyl)borate, dimethyl ferroceniumtetrakis(pentafluorophenyl)borate, and silvertetrakis(pentafluorophenyl)borate.
 5. The catalyst composition asclaimed in claim 1, wherein the activating cocatalyst is methylaluminoxane.
 6. The catalyst composition as claimed in claim 1, whereinthe activating cocatalyst is a mixture of a trialkyl aluminum and aborate.
 7. A process for preparing a syndiotactic vinyl aromatic polymercomprising subjecting one or more vinyl aromatic monomers topolymerization in the presence of a catalytically effective amount ofthe bidentate coordinated catalyst composition as set forth in claim 1.8. The process as claimed in claim 7, wherein the vinyl aromatic monomeris represented by the formula (II): ##STR3## wherein each R² isindependently selected from hydrogen; aliphatic, cycloaliphatic,aromatic hydrocarbon groups having from 1 to 10 carbon atoms; andhalogen atoms.
 9. The process as claimed in claim 8, wherein the vinylaromatic monomer is styrene.
 10. The catalyst composition as claimed inclaim 1, wherein the bidentate ligand (BD) is selected from the groupconsisting of: ##STR4## wherein R¹ is alkyl having from 1 to 6 carbonsatoms.
 11. The catalyst composition as claimed in claim 1, wherein metalcomplex is selected from the group consisting of:(η⁵ --C₅ H₅)Ti(C₆ H₄--o--CH₂ NMe₂)₂ ; (η⁵ --C₅ Me₅)Ti(C₆ H₄ --o--CH₂ NMe₂)₂ ; (η⁵ --C₅H₅)Ti(CH₂ C₆ H₄ --o--NMe₂)₂ ; (η⁵ --C₅ Me₅)Ti(CH₂ C₆ H₄ --o--NMe₂)₂ ;(η⁵ --C₅ H₅)Ti(OC₆ H₄ --o--NMe₂)₂ ; (η⁵ --C₅ Me₅)Ti(OC₆ H₄ --o--NMe₂)₂ ;(η⁵ --C₅ H₅)Ti(C₆ H₄ --o--OCH₃)₂ ; (η⁵ --C₅ Me₅)Ti(C₆ H₄ --o--OCH₃)₂ ;(η⁵ --C₅ H₅)Ti(9-hydroxy-N,N-dimethyl-1-naphthylamine)₂ ; (η⁵ --C₅Me₅)Ti(9-hydroxy-N,N-dimethyl-1-naphthylamine)₂ ; (η⁵ --C₅H₅)Ti(8-hydroxyquinoline)₂ ; (η⁵ --C₅ Me₅)Ti(8-hydroxyquinoline)₂ ; (η⁵--C₅ H₅)Ti(acetylacetone)₂ ; and (η⁵ --C₅ Me₅)Ti(acetylacetone)₂.